1. Field of the Invention
This invention relates generally to electronic identification and recognition systems and more specifically to such systems wherein it is not necessary to make physical contact between the identification card and the recognition apparatus, and the identifier is operable by a portable internal power source.
2. Description of the Prior Art
There are various electronic identification and recognition systems wherein the identifying device is portable. Sometimes the identifying device is referred to as a "card," "tag," "key," or the like. The recognition station or reader station is prepared to recognize identifying devices of predetermined characteristics when such identifying device is brought within the proximity of the reader station. Mutual coupling takes place between the two devices when they are proximate to one another and it is not necessary to bring the device into physical contact. The identifying device may contain a battery, though it usually receives its energy from the reader station.
Uses for such systems may include identification of persons having identifying devices in their possession. For example, the identifying device may take the shape of a credit card and have an electronic circuit embedded therein for radiating signals of identifying intelligence. An individual possessing the card may position it adjacent a door that the individual desires to enter. A recognition device may be arranged to control the door latch and if it recognizes radiating signals of certain predetermined intelligence, the door latch responds to the reader when the individual places the "card" proximate to the reader. Other uses for such systems include having the identifier in the form of a tag attached to a vehicle to be identified. As the vehicle passes a certain location, its identification is recognized and recorded. Also, in production lines, garments or other items may carry identifying tags so that they can be appropriately processed as they are recognized along various points in the production processes.
The prior art includes various patents and patent application by the present inventor. The patents include U.S. Pat. No. 4,223,830 for "Identification System", issued Sept. 23, 1980; U.S. Pat. No. 4,236,068 for "Personal Identification and Signalling System", issued Nov. 25, 1980; U.S. Pat. No. 4,384,288 for "Portable Radio Frequency Emitting Identifier", filed on Dec. 31, 1980; U.S. Pat. No. 4,459,474 for "Identification System with Separation and Direction Capability and Improved Noise Rejection", filed on May 18, 1981; U.S. Pat. No. 4,388,524 for "Electronic Identification and Recognition with Code Changeable Reactance", filed on Sept. 16, 1981; U.S. Pat. No. 4,473,825 for "Electronic Identification System with Power Input-Output Interlock and Increased Capabilities", filed on Mar. 5, 1982; U.S. Pat. Ser. No. 4,546,241 for "Identification System with Synchronous Modulation of Return Signal", filed Dec. 10, 1982; U.S. Pat. No. 4,580,041 for "Electronic Proximity Identification System with Low Power Identifier, Simplified", filed on Dec. 9, 1983; U.S. Pat. No. 4,600,829 for "Electronic Proximity Identification and Recognition System with Isolated Two-Way Coupling", filed on Apr. 2, 1984.
In the electronic portable recognition and identification systems of the prior art, the power for the identifier comes from either an internal battery, or from mutually coupled power between the reader and the identifier. Both of these methods have some problems. The prior art systems which use a battery require the battery to power both a clock and a radio frequency oscillator. The large power requirements of the radio frequency oscillator rapidly drains the battery. Thus, the battery operated identifiers of the prior art have a limited life. Some of the prior art shows identifiers which are powered by mutual coupling. However, if mutual coupling is used, the range is limited because of the difficulty of coupling sufficient power over distances.